Changes in balance performance and Its determining factors in the lower leg during the competition season in adolescent football players

The aim of our study was to evaluate changes in static and dynamic balance, shin muscle strength, active and passive ankle range of movement (ROM), and foot kinesthetic acuity during the first 8 weeks of the competitive season in male adolescent football players. Thirteen players (age 15.26 ± 0.93 years, Tanner stages 3–4) participated. Static and dynamic single-leg balance and foot kinesthetic sense were assessed using a stabilometric platform. Ankle plantarflexion–dorsiflexion and inversion–eversion ROM were measured with a goniometer. Peak isometric force of the ankle plantar flexors, dorsiflexors, invertors, and evertors was measured with a handheld dynamometer, and peak torque was calculated as force × lever arm length. Eight weeks of competitive period was associated with static balance improvement: mean anterior-posterior and medial-lateral sway speeds decreased bilaterally ( P = 0.024). Center of pressure (CoP) perimeter decreased significantly in the non-dominant (N) leg ( P = 0.028). CoP perimeter and sway speed were positively correlated with passive dorsiflexion/plantarflexion ROM, and CoP ellipse area was correlated with active plantarflexion ROM ( P ≤ 0.049). Dynamic balance improvement: the trunk total standard deviation (TTD) angle decreased when standing on the dominant (D) and N legs ( P ≤ 0.018). TTD angle was negatively correlated with peak ankle dorsiflexion, eversion, and inversion torques ( P ≤ 0.039). Passive plantarflexion ROM decreased bilaterally (P ≤ 0.04), whereas active ROM remained unchanged ( P ≥ 0.05). Absolute and relative peak isometric dorsiflexion torques increased bilaterally ( P ≤ 0.003), but side asymmetry (higher plantar- and dorsiflexion torques in the D leg) persisted ( P ≤ 0.045). Mean kinesthetic sense error was lower with the D leg, whereas trial completion time was shorter with the N leg in both sessions ( P ≤ 0.032).